alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Win32/TrojanDownloader.Agent.FC CnC Activity"; flow:established,to_server; http.start; content:"POST /loader/gate HTTP/1.0|0d 0a|Host|3a 20|"; fast_pattern; http.user_agent; content:!"|20|"; http.referer; content:!"|2e|"; http.request_body; content:"data="; startswith; pcre:"/^(?:[a-zA-Z0-9+/]{4})*(?:[a-zA-Z0-9+/]{2}==|[a-zA-Z0-9+/]{3}=|[a-zA-Z0-9+/]{4})$/R"; reference:md5,d8dbaecab080b40e7782b10affb630f4; classtype:command-and-control; sid:2030678; rev:1; metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2020_08_12, deployment Perimeter, malware_family Win32_TrojanDownloader_Agent_FC, performance_impact Low, confidence High, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_08_12;)